Angiopoietin 2 Is Associated with Vascular Necroptosis Induction in Coronavirus Disease 2019 Acute Respiratory Distress Syndrome.

Vascular injury is a well-established, disease-modifying factor in acute respiratory distress syndrome (ARDS) pathogenesis. Recently, coronavirus disease 2019 (COVID-19)-induced injury to the vascular compartment has been linked to complement activation, microvascular thrombosis, and dysregulated immune responses. This study sought to assess whether aberrant vascular activation in this prothrombotic context was associated with the induction of necroptotic vascular cell death. To achieve this, proteomic analysis was performed on blood samples from COVID-19 subjects at distinct time points during ARDS pathogenesis (hospitalized at risk, N = 59; ARDS, N = 31; and recovery, N = 12). Assessment of circulating vascular markers in the at-risk cohort revealed a signature of low vascular protein abundance that tracked with low platelet levels and increased mortality. This signature was replicated in the ARDS cohort and correlated with increased plasma angiopoietin 2 levels. COVID-19 ARDS lung autopsy immunostaining confirmed a link between vascular injury (angiopoietin 2) and platelet-rich microthrombi (CD61) and induction of necrotic cell death [phosphorylated mixed lineage kinase domain-like (pMLKL)]. Among recovery subjects, the vascular signature identified patients with poor functional outcomes. Taken together, this vascular injury signature was associated with low platelet levels and increased mortality and can be used to identify ARDS patients most likely to benefit from vascular targeted therapies.

Tie2 activation protects against prothrombotic endothelial dysfunction in COVID-19.

Endothelial dysfunction accompanies the microvascular thrombosis commonly observed in severe COVID-19. Constitutively, the endothelial surface is anticoagulant, a property maintained at least in part via signaling through the Tie2 receptor. During inflammation, the Tie2 antagonist angiopoietin-2 (Angpt-2) is released from endothelial cells and inhibits Tie2, promoting a prothrombotic phenotypic shift. We sought to assess whether severe COVID-19 is associated with procoagulant endothelial dysfunction and alterations in the Tie2/angiopoietin axis. Primary HUVECs treated with plasma from patients with severe COVID-19 upregulated the expression of thromboinflammatory genes, inhibited the expression of antithrombotic genes, and promoted coagulation on the endothelial surface. Pharmacologic activation of Tie2 with the small molecule AKB-9778 reversed the prothrombotic state induced by COVID-19 plasma in primary endothelial cells. Lung autopsies from patients with COVID-19 demonstrated a prothrombotic endothelial signature. Assessment of circulating endothelial markers in a cohort of 98 patients with mild, moderate, or severe COVID-19 revealed endothelial dysfunction indicative of a prothrombotic state. Angpt-2 concentrations rose with increasing disease severity, and the highest levels were associated with worse survival. These data highlight the disruption of Tie2/angiopoietin signaling and procoagulant changes in endothelial cells in severe COVID-19. Our findings provide rationale for current trials of Tie2-activating therapy with AKB-9778 in COVID-19.

The role of angiopoietin-2 and surfactant protein-D levels in SARS-CoV-2-related lung injury: A prospective, observational, cohort study.

INTRODUCTION: Coronavirus disease-2019 (COVID-19) is a respiratory disease whose clinical manifestation ranges from asymptomatic to severe respiratory failure. The purpose of this study was to investigate the place of serum surfactant-D (SP-D) and angiopoetin-2 (Ang-2) levels in predicting severity of disease in patients diagnosed with COVID-19. METHODS: Sixty-four patients diagnosed with COVID-19 between September 2020 and February 2021, 50 patients diagnosed with community-acquired pneumonia and a 50-member healthy control group were included in the study. Plasma samples and clinical data were collected within 72 h after admission, during hospital stay. Serum SP-D and Ang-2 concentrations were measured using the enzyme-linked immunosorbent assay. RESULTS: SP-D and Ang-2 levels were significantly higher in the mild-moderate pneumonia and severe/critical patient groups compared to the asymptomatic and noncomplicated COVID-19 patients (p < 0.001 for all groups). Serum SP-D and Ang-2 levels of severe-critical COVID-19 patients were significantly higher than CAP patients (p < 0.001). Powerful correlation was present between clinical severity of COVID-19 and SP-D and Ang-2 levels (r = 0.885 p < 0.001 and r = 0.913 p < 0.001, respectively). Cut-off values of 37.7 ng/ml (AUC = 0.763, p < 0.001, 95% confidence interval [CI] = 0.667-0.860) for SP-D and 4208.3 pg/ml (AUC = 0.659, p = 0.004, 95% CI = 0.554-0.763) for Ang-2 were identified as predictors of COVID-19 disease at receiver operating characteristic curve analysis. CONCLUSION: SP-D and Ang-2 are predictive factors in differentiating COVID-19 patients and determining severity of disease. These data may be important for the initiation of treatment in the early stage of the disease in patients with COVID-19.

Concentrated Secretome of Adipose Stromal Cells Limits Influenza A Virus-Induced Lung Injury in Mice.

Despite vaccination and antivirals, influenza remains a communicable disease of high burden, with limited therapeutic options available to patients that develop complications. Here, we report the development and preclinical characterization of Adipose Stromal Cell (ASC) concentrated secretome (CS), generated by process adaptable to current Good Manufacturing Practices (cGMP) standards. We demonstrate that ASC-CS limits pulmonary histopathological changes, infiltration of inflammatory cells, protein leak, water accumulation, and arterial oxygen saturation (spO2) reduction in murine model of lung infection with influenza A virus (IAV) when first administered six days post-infection. The ability to limit lung injury is sustained in ASC-CS preparations stored at -80 °C for three years. Priming of the ASC with inflammatory factors TNFα and IFNγ enhances ASC-CS ability to suppress lung injury. IAV infection is associated with dramatic increases in programmed cell death ligand (PDL1) and angiopoietin 2 (Angpt2) levels. ASC-CS application significantly reduces both PDL1 and Angpt2 levels. Neutralization of PDL1 with anti-mouse PDL1 antibody starting Day6 onward effectively ablates lung PDL1, but only non-significantly reduces Angpt2 release. Most importantly, late-phase PDL1 neutralization results in negligible suppression of protein leakage and inflammatory cell infiltration, suggesting that suppression of PDL1 does not play a critical role in ASC-CS therapeutic effects.